You should be fine but you may not have video acceleration, etc… The 64 bit ISO doesn’t have the virtual box kernel modules installed, I believe this was done to conserve disk space, the 32 bit ISO does have them, once you install the system to virtual box you may want to install this package:
sudo pacman -S linux310-virtualbox-guest-modules
I just ran the 64 bit ISO in a VM and the 64 bit ISO does have the linux310-virtualbox-guest-modules installed. Installing the system to the virtual hard disk, also installs this package.
I set up the guest machine with 128 MB of video memory and enabled 3D acceleration, however I could not get KDE to accept the use of OpenGL. For my uses, I do not need 3D acceleration, so this is of no consequence to me.